In the manufacture of tires and in particular pneumatic tires used for passenger vehicles, trucks, etc., the tires are subjected to a tire rolling resistance measurement test to insure that the same meet certain test standards. These measurements normally are taken by bringing a freely rotatably mounted tire into contact with a driven load wheel or wheels, and by the use of load cells calculate the amount of resistance to the rolling movement of the tire. These prior art tire testing apparatus require numerous load cell calibrations and checks as well as various computations in order to insure that the test results are accurate.
One factor effecting these prior art test results is the friction that is naturally present in the bearing mountings of both the test tire and the load wheel or wheels. The friction present in the various bearings have a definite effect on the accuracy of the tests being performed. These friction forces provide an inherent error in the tire test machine or apparatus. Therefore, to obtain more accurate tests, the friction losses must be measured by the use of load cells or other devices for each tire test machine and for each of the various sizes of tires being tested, as well as for the various rotational speeds at which the tests are being perfomred. These determinations have to be checked periodically due to the natural changes in the friction forces as the testing apparatus and associated mounting bearings age and wear throughout the life of the apparatus. All of these tests and calculations increase considerably the time and cost of performing the rolling resistance tests on the tires.
Some examples of prior art tire testing machines and apparatus are shown in U.S. Pat. Nos. 3,498,125; 3,543,576; 3,948,095; 4,171,641; 4,233,838; 4,238,954 and 4,324,128. However, none of these known prior art tire test machines and apparatus provide any means for negating the undesirable effect of the friction forces in the bearings as achieved by my invention hereinafter described.
Certain prior art devices have been developed for negating the influence of bearing friction, none of which, however, have been used or proposed for use in tire test equipment.
U.S. Pat. No. 3,167,958 shows a support arrangement for a flow meter wherein the same is provided with eccentric bearing supports and a mounting arrangement which will prevent or reduce friction loss because the outer rotary element is slaved to the inner rotary element whereby little or no movement takes place in the inner rotary element relative to the outer rotary means. A somewhat similar bearing arrangement with respect to a center shaft is shown in U.S. Pat. No. 3,365,596.
U.S. Pat. Nos. 2,577,942; 2,970,480 and 2,983,556 show devices which attempt to eliminate a bearing friction problem in the gyroscope art wherein the gyroscope support utilizes concentrically disposed bearing supports to lessen or eliminate this problem of bearing friction.
U.S. Pat. No. 4,235,092 discloses an apparatus for measuring the running torque of a bearing under a radial load by utilizing a balanced radial force on the bearing.
U.S. Pat. Nos. 3,116,628; 3,715,909 and 4,038,863 disclose various apparatus and devices for measuring bearing friction, none of which propose the particular solution to eliminating such bearing friction as in my invention.